powerpc/papr_scm: Fix DIMM device registration race

oohal · mpe · commit b0d65a8cbcb0 · 2018-12-09T21:32:30.000+11:00
When a new nvdimm device is registered with libnvdimm via nvdimm_create() it is added as a device on the nvdimm bus. The probe function for the DIMM driver is potentially quite slow so actually registering and probing the device is done in an async domain rather than immediately after device creation. This can result in a race where the region device (created 2nd) is probed first and fails to activate at boot. To fix this we use the same approach as the ACPI/NFIT driver which is to check that all the DIMM devices registered successfully. LibNVDIMM provides the nvdimm_bus_count_dimms() function which synchronises with the async domain and verifies that the dimm was successfully registered with the bus. If either of these does not occur then we bail. Fixes: b5beae5 ("powerpc/pseries: Add driver for PAPR SCM regions") Signed-off-by: Oliver O'Halloran <oohall@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -223,6 +223,9 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)
 		goto err;
 	}
 
+	if (nvdimm_bus_check_dimm_count(p->bus, 1))
+		goto err;
+
 	/* now add the region */
 
 	memset(&mapping, 0, sizeof(mapping));

Original file line number	Diff line number	Diff line change
`@@ -223,6 +223,9 @@ static int papr_scm_nvdimm_init(struct papr_scm_priv *p)`
`223`	`223`	`goto err;`
`224`	`224`	`}`
`225`	`225`
	`226`	`+ if (nvdimm_bus_check_dimm_count(p->bus, 1))`
	`227`	`+ goto err;`
	`228`	`+`
`226`	`229`	`/* now add the region */`
`227`	`230`
`228`	`231`	`memset(&mapping, 0, sizeof(mapping));`